I was chatting with a friend about this and that the other day. It was a lovely evening and we were admiring some cirrrus clouds that were just catching the edge of the sunset, and it was all very beautiful. I can’t rememeber the exact sequence of the conversation that led to this point, but the Museum of Curiosity cropped up. I had recently been listening to series to on Radio 4 extra and Gavin Pretor-Pinney, the founder of the Cloud Appreciation Society had been on. He actually donated Kelvin-Helmholtz clouds to the Museum, but there was a wonderful discussion around the length of time that it would take to fall through a cloud. Without getting too distracted, one poor parachutist who fell through a cumulonimbus cloud took around 40 minutes to escape – it should have been a few minutes at most, but he got buffeted about by the internal winds, and his parachute deployed because of the variation in pressure within the cloud and he got sucked back upwards more than once.
And then my friend came out with the brilliant piece of information that an “average” cloud weighs as much as 88 elephants. The obvious response to this was “African or Asian?”, but she couldn’t remember. My default in such situations is to assume an African bull elephant, which typically weighs in at 6,000 kg (or 6 tonnes). On this basis then, we quickly worked out that a cloud would weigh 528,000 kg. Given that a tonne of water at sealevel is 1 cubic metre in volume, and that an Olympic sized swimming pool contains 2,500 cubic metres of water, we can deduce that we would need five clouds to fill an Olympic swimming pool.
Because we weren’t entirely sure of the grounding for this, we did what any sensible people having a conversation would do. She went home and checked the book where she’d got this information from, and I turned to the internet. It turned out she’d misremembered very slightly, and the book stated 80 elephants, and it specified Asian, with an average weight of 2,500 kg. On the other hand, Google quickly provided me with a long list of web-pages – apparently weighing clouds is an actual thing. This of course meant that I rapidly lost interest, because someone’s done all this before. Further, I have no desire to step on the toes of people who do this sort of thing for a living. That said, as ever there is a wild discrepency: the book is suggesting that an average cloud is 200,000 kg, whilst one source I looked at was closer to my suggestion, coming in at 500,000 kg. They used a more generic African elephant in there visualisation,and so cam in at 100 elephants.
So for me, there are two things that we can get from this. Firstly, it appears that we need to have an internationally agreed elephant reference. I suspect that the Systém Internationale would not be interested in this, given that we have a perfectly usuable kg, but it is nice to have reference points that everybody can understand, especially when you are dealing with big numbers. Secondly, and perhaps more importantly, we can now develop the game of looking at clouds and saying what it looks like – we can add how much water we think it contains, and how many elephants it equates to.